Architects and stonemasons, huge palace and temple clusters were built

woohoo921
Both the phrases you are citing are noun modifiers, but they are different variations. Note that in the second example, we don't see "a jazz pianist." When we just see "Baseball legend Hank Aaron" or "Academy Award winner Lupita Nyong'o," we are just adding a descriptor to clarify who the person is. When we start with a noun phrase followed by a comma--"A gifted dancer," "Trained at Harvard," "A cousin of the salamander," "A friend of mine," "Immoral scoundrels"--etc., we are adding detail to the main noun that may not be helpful in narrowing down whom we are talking about, but does relate to the action that follows. In some ways, these almost work the way that initial adverbial modifiers do, in that they tend to provide insight into how or why the action described was undertaken. For instance, we could say "Baseball legend Hank Aaron died last week." He didn't die because he was a legend; that part just clarifies who he is. It would be odd to say "A baseball legend, Hank Aaron died last week." It almost sounds like his baseball ability had something to do with his death, and that doesn't really make sense. We also wouldn't say "Trained at Harvard, she is my wife's cousin." There's no connection that justifies the inclusion of that initial modifier.

It's hard to make an absolute rule out of any of this, since there are so many reasons to use commas, but hopefully this rough distinction helps. There are cases where a comma seems to make no difference: "My best friend Jay was the minister at our wedding" doesn't differ much in meaning from "My best friend, Jay was the minister at our wedding." We also have to distinguish this from cases where the part after the comma is itself a modifier followed by a comma: "My best friend, Jay, is visiting this weekend." In that case "My best friend" is the subject and "Jay" is just telling us his name.

I hope this helps!